In electrophotography, a uniform electrostatic charge is initially applied to the surface of a photoconductive layer. This charge is then selectively dissipated in accordance with a particular pattern as determined by exposure of the photoconductive layer surface to a light image. The resulting charge pattern therefore defines an electrostatic latent image upon the photoconductive layer. This latent image may then be rendered visible by applying electrostatically charged toner particles to the photoconductive layer, the toner particles adhering to the photoconductive layer surface by means of electrostatic attraction. In turn, the visible image may now be rendered permanent by subjecting the toner particles to a heating process which fuses the particles to the photoconductive layer.
As is well-known, in accordance with the conventionally acceptable developing method utilizing a liquid developer or toner, which comprises a liquid carrier for finely divided electrostatic toner particles, such as, for example, carbon particles, suspended therein, the electrophotographic element or image-exposed film is initially dipped within the liquid toner so as to produce the visible image thereon which of course corresponds to the originally defined latent image. While this development method has of course proven to be quite satisfactory for some types of systems and film, it is simply not feasible or applicable for the specialized type of system in which the imaging and developing are to be automatically accomplished within a single piece of apparatus. A microphotographic copying machine in which data from successive documents is sequentially recorded upon individual frames of a multi-frame microfiche is an exemplary embodiment of the aforenoted specialized type of apparatus.
In addition, in view of the fact that it is desirable to rapidly image and develop each frame prior to, or partially co-extensive with, the processing of the next succeeding frame, the image development process must, of necessity, be one which can be accomplished quickly and conveniently with respect to, for example, a microfiche, strip or roll film, or aperture card, fixed within a suitable holder or support means within the reproduction apparatus. In particular, the developing system must be capable of quickly and accurately applying the correct amount of developer or toner to the imaged area of the electrophotographic film, as well as removing the excess toner from the film without permitting leakage of the toner particles either into the interior portion of the reproduction apparatus, or onto other areas of the film which have already been imaged or have not as yet been imaged. Still further, the development system must be capable of rapidly evaporating or partially drying any portion of the toner carrier liquid remaining upon the film so as to in fact immobilize the toner particles adhering to the film and thereby prevent any smearing of the toned or visible image.
The foregoing characteristics and objectives have been addressed and substantially achieved in a currently commercially available viable record processor apparatus known as the System 200 which is manufactured and distributed by A. B. Dick/Scott of South Hadley, Mass. This system is embodied within U.S. Pat. Nos. 4,141,647 issued to George D. Lempke and Nils L. Hakanson; 4,047,950 issued to Frank C. Gross; 3,972,610 issued to Frank C. Gross; 3,927,639 issued to the present inventor-applicant of this application, John D. Plumadore; and 3,916,828 issued to Frank C. Gross. All of these patents are concerned, in their entirety, or at least in part, with toner flow control systems wherein, for example, the microfiche, film card, or the like, is disposed within a vertical plane angularly located 90.degree. relative to a horizontal plane. In turn, therefore, when the liquid toner or developer is conducted into fluidic contact with the particular portion of the microfiche or the like being toned or developed, the liquid toner will of necessity be flowing in a vertical plane path.
Thus, while the System 200 comprises viable record processor apparatus, it is apparent that the definition of the toner cell, from the viewpoint of the control of the liquid toner flow characteristics, is necessarily quite complex. Due to the flow of the liquid toner across the face of the photographic element being developed within the vertical plane, as noted hereinbefore, the liquid toner will tend to flow down the full extent of the photographic element or film unless substantial negative pressure or vacuum control means are employed for, in effect, sucking the excess toner off of and away from the film surface. In addition, complex sealing means are often also employed for assuring the appropriate definition of the toner cell. Such sealing means usually comprise components which are movable toward, and retractable away from, the film surface. Such means must be accurately operated and actuated so as not to result in the production of smeared images. Still further, due to the uncontrolled flow of the liquid toner within the vertical plane under the influence of gravity, as well as the vacuum-suction or negative air pressure being impressed upon the liquid toner, nonuniform imaging has also been experienced.
In addition to the aforenoted vertically oriented photographic element systems, and the toner flow control means operatively associated therewith, horizontally disposed photographic element development systems have also been proposed, however, these have proven to be as operationally complex as the vertical systems. As will be readily appreciated, within a system wherein the photographic element being developed is disposed within a horizontal plane while the liquid toner is caused to flow thereover for development of the latent image thereon, there is no natural, that is, gravitational, flow of the toner. Again, therefore, in order to properly control the flow of the liquid toner, substantial pressure differentials must in fact be established. In addition, when liquid toner is caused to flow within a horizontal plane, air bubbles tend to become trapped therein thereby deleteriously affecting the developed image from the viewpoint of image uniformity.
A need therefore exists for an improved toner flow control system for use in developing an electrostatic latent image upon an electrophotographic film or element whereby the liquid toner flow characteristics or parameters can be easily controlled and the toner cell definition easily achieved.
Accordingly, it is an object of the present invention to provide a new and improved toner flow control system for liquid toner utilized for developing an electrostatic latent image upon an electrophotographic element.
Another object of the present invention is to provide a new and improved toner flow control system for liquid toner utilized in developing an electrostatic latent image upon an electrophotographic element which overcomes the operational disadvantages and drawbacks characteristic of similar conventional toner flow control systems.
Still another object of the present invention is to provide a new and improved toner flow control system for liquid toner utilized in developing an electrostatic latent image upon an electrophotographic element whereby the flow of the liquid toner relative to the portion of the electrophotographic element being developed can be accurately and simply controlled.
Yet another object of the present invention is to provide a new and improved toner flow control system for liquid toner utilized for developing an electrostatic latent image upon an electrophotographic element wherein the flow of the liquid toner relative to the portion of the electrophotographic element being developed can be operationally controlled without the requirement of vacuum suction means or the establishment of substantial differential pressure zones.
Yet still another object of the present invention is to provide a new and improved toner flow control system for liquid toner utilized for developing an electrostatic latent image upon an electrophotographic element wherein the flow of the liquid toner relative to the portion of the electrophotographic element being developed can be operationally controlled such that uniform imaging upon the electrophotographic element portion being developed is achieved.
Still yet another object of the present invention is to provide a new and improved toner flow control system for liquid toner utilized for developing an electrostatic latent image upon an electrophotographic element wherein the flow of the liquid toner relative to the portion of the electrophotographic element being developed can be operationally controlled in such a manner so as to provide sufficient toner cell definition without the requirement of auxiliary complex element-contacting sealing means.
A further object of the present invention is to provide a new and improved toner flow control system for liquid toner utilized for developing an electrostatic latent image upon an electrophotographic element wherein there is provided means for rapidly evaporating residual or excess toner carrier liquid remaining upon the film element after toning has been achieved.
A still further object of the present invention is to provide a new and improved toner flow control system for liquid toner utilized for developing an electrostatic latent image upon an electrophotographic element wherein the aforenoted means for evaporating the residual toner carrier liquid is also provided for seating the element film upon the pressure plate of the support means or holder of the reproduction apparatus as well as for aiding in the toner cell definition.
A yet further object of the present invention is to provide a new and improved toner flow control system for liquid toner utilized for developing an electrostatic latent image upon an electrophotographic element which is substantially simple in design and in its structural components interrelationships so as to render the manufacturing costs of this toner system within the overall camera/processor apparatus relatively low.